Herewith is my musing on what the Fall of Man consisted of, seen through both scientific and theological lenses to give what I hope is stereoscopic vision.
Let us posit some people, homo sapiens to be precise, as we understand them to be. Note that for the purposes of this discussion, it doesn't matter whether our species had been evolving for millennia or whether God created the first two prototypes by special creation -- the people we're talking about are people like us in all respects. You can call them "Adam" and "Eve" if you like, though those seem to be titles, rather than personal names. "Fred" and "Wilma" will do as well. The Bible talks of these two only, though that may be a case of compression. I'm not sure that it would matter if there were a small community of these people.
But whether there are only these two or a lot of them wandering around scratching themselves, these are the first to "wake up" to God. These are the ones of whom it is said, "then the Lord God . . . breathed into his nostrils the breath of life; and man became a living being." Now, in one sense, everything that lives by breathing is a living being in the same sense -- nothing special about humanity. But if this is a metaphor for humanity being capable of enjoying a relationship with God (in a way that, say, snails are not), then that's something special.
So these two are the very first to understand themselves as Selves and to understand God as the fulfillment of their Selves. And they very properly want to please God, Him-who-is-out-there-and-inside-us-at-th
What they are discovering is what I call the Oughtness of Life. Given that God IS, and that I NEED, how OUGHT I to live my life? The rules are simple: don't do X. Do not eat of the tree of the knowledge of good and evil. They agree that the rule is good, and it seems simple enough to obey it.
And then, they don't. The traditional view is that they freely chose to do something which eliminated their freedom, and the freedom of all their descendants. I'm going to suggest that though their choice was not predetermined, it was inevitable. Human beings -- Selves -- in the very act of understanding what they OUGHT to do, find that they are incapable of doing it completely and correctly. The moral sense that separates us from, say, cats and dogs, comes up against a moral failure that accrues to us only because we knew we were supposed to do something that we cannot, even when we wished to.
In Dorothy Sayers' play, "The Devil to Pay," Faust asks the Devil, "What art thou, Mephistopheles?" To which the Devil replies, "I am the price that all things pay for being,/ The shadow on the world, thrown by the world/ Standing in its own light, which light God is./ So first, when matter was, I was called Change./ And next, when life began, I was called Pain,/ And last, when knowledge was, I was called Evil . . ."
Human beings cannot, of their own limited nature, do what they know they ought to do. Cats and dogs couldn't either, but then they're not trying. Because we know we should, and know we can't (or, at least, DON'T), we experience our limitation as evil -- our naturally good bodies are sources of shame; our relationship with each other is a source of blame; our relationship with a loving God is a source of fear; and so on. Trying to understand good and evil means, for us, experience good as evil.
So Original Sin is not heritable; it just is. We cannot be what we know we should be. In this sense, the Fall of Man -- of Adam and Eve or Fred and Wilma -- was inevitable. God made us limited, and in discovering our limits, we discovered our own moral failure.
Now, if God damned us for this, and this alone, I can see a lot of complaint. But our inherent limitation is not the same as our fault, and all of us have that in plenty. We have not merely fallen short; we have decided that other goals have been more desirable than the goal of living as we ought. And for this, we are at fault.
Original Sin separates us from God, because we cannot live as we know God desires us to, and that means that we cannot know him as we ought -- the relationship has a serious handicap. But actual sin separates us from God, because we choose to live as we ought not, and this offends him. Each of us further damages the relationship between ourselves and God.
Jesus was born into the family of homo sapiens to reconcile us to God. By his sacrifice he reconciles us to God, removing the actual sins which separate us from the Father. But he also makes it possible for us to finally do what we know we ought to do; by his Spirit (and through the eventual resurrection of all flesh) he will make us fit for God's company. In this way, he repairs Original Sin.
Anyway, to recapitulate, the ability to know God and the inability to obey God are two sides of the same coin. In the same act of knowing the rules, our first parents disobeyed them. The "waking up" to God and the Oughtness of Life is inseparable from the "death" that accompanies our moral failure and which makes our physical deaths so intolerable to us. God, creating us as we are, knew that we would fail and fall -- did not, indeed DESIRE us to do so, but knew that we would -- and therefore foresaw the need for the cross in the first act of creation.